920 
species the four ventral cells would be larger than the four dorsal 
ones. Nothing of the kind proves to be true: the eight-celled stages in 
Rana fusca and esculenta are nearly uniform. Besides, we saw in 
the foregoing communication, how relatively independent the direction 
of the first cleavages is of the internal constitution of the egg. 
Chemistry. — ‘“hintgen-investigation of allotropic forms”. (Preli- 
minary communication). By Dr. J. Our Jr. and Dr. A. J. Bust. 
(Communicated by Dr. Ernst Conen). 
(Communicated in the meeting of January 27, 1917.) 
Drsye and Screrrer have in the “Nachrichten der Königlichen 
Geschellschaft der Wissenschaften zu Göttingen” *) published their 
investigations about “Interferenzen an regellos orientierten Teilchen 
in Röntgenlicht”. Led by theoretic considerations DerByr *) had come 
to the conclusion that secondary Röntgenlight, emitted by a body 
shone upon by Röntgenlight is not equally strong in every direction. 
The arrangement of the electrons in the atoms must necessarily 
give to that light a maximum of intensity in certain definite directions. 
Even if the atoms should not be arranged regularly, the resultant 
of all secondary light-emission will be a definite division of the 
light in space into maxima and minima of intensity. 
DeByr expected and actually obtained in his investigations with 
SCHERRER results, which clearly proved the existence of such a 
division of lightrays (interference). But by the side of the pheno- 
menon he expected he noticed in several cases, whenever crystalline 
material had been used for the investigation, a much more striking 
phenomenon. Besides the diffuse maxima, which were visible in the 
photos as so many spots with vague outlines, there were to be seen 
some rather distinct lines, which made one think of a spectrum. 
Desye and ScHERRER pointed out that this should not be explained 
from the interference of the Röntgen rays in the electron-complex 
of the atom, but in an analogous way from the interference of those 
rays falling upon the crystalline structure that are to be formed in 
the macroscopically unarranged mass.*) This is contrary to the 
generally accepted opinion that Röntgen-interference images can only 
be obtained with large and properly-shaped crystals. From the 
theoretical considerations as well as from experiments it becomes 
1) Mathem-physikal. Klasse 1916 Heft 1. See also Phys. Zeitschr. 17, 277 (1916). 
*) Nachr. der K. Ges. der Wissensch. in Göttingen math.-physikal Klasse 1915. 
5) Fine crystalpowder or quasi amorphous material. 
